Landing shock absorber



July 5, 1949. G. CHAUSSON LANDING SHOCK ABSORBER 4 Sheets$heet 1 Filed Nov. 30, 1945 Jufiy 5, 1949. CHAUSSON 2,475,477

LANDING SHOCK ABSORBER Filed NOV. 50, 1945 4 Sheets-Shee'l: 2

Juliy 5, 11949. G. cHAussoN LANDING SHOCK ABSORBER Filed NOV. 30, 1945* 4 Sheets-Sheet 3 as/L U rJJ/z July 5, i949.

G. cHAussoN LANDING SHOCK ABSORBER 4 Sheets-Sheet 4 Filed Nov. 50, 1945 Patented July 5, 1349 LANDING SHOCK ABSORBER Gaston Chausson, Asnieres, France, assignor to Societe Anonyme des Usines Chausson, Asnieres, France, a company of France Application November 30, 1945, Serial No. 631,890 In France February 25, 1944 Section 1, Public Law 690, August 8, 1946 Patent expires February 25, 1964 9 Claims. 1

This invention has for its object a device dissipating any kind of energy by the throttling of a fluid by ensuring a substantially constant reaction throughout the course of its operation. Said device is so arranged that the value of said reaction and, consequently, of the energy dissipated, is adjusted in function of the energy to be absorbed.

Although this device can be applied to any apparatus in which a violent impulse is directly transmitted to a mass of fluid, it can be constructed, in a particularly advantageous manner, in the form of a landing shock-absorber for airplanes, in which it allows optimum regularization of the absorption of the vertical energy of the airplane, throughout the stroke of said shock-absorber, whose action thus remains constant, so that use can be made, for ensuring the suspension of the airplane, of a resilient member of slight reaction, restituting, during the return stroke, but a small fraction of the energy to be absorbed.

In an energy dissipating device according to the invention, a piston sliding in a cylinder containing a liquid mass, under the action of a stress exerted on its rod and/or on the cylinder, comprises an adjusting obturator held applied on its seat in antagonism to the action of the delivery pressure during the first part of the delivery stroke of said piston by a pressure at least equal to that prevailing at that moment in the delivery chamber of the cylinder, which is generated in a balancing chamber provided in the piston, the liquid being delivered, during said first part of the delivery stroke of the piston, through ducts of small cross-section or a calibrated conduit ensuring a suitable loss of pressure, whereas during the second part of the delivery stroke the piston obturates said ducts or said calibrated conduits, then the balancing chamber is maintained under the pressure prevailing therein at the end of the first part of the piston stroke, so that the obturator opens under the action of the increased pressure generated in front of the piston, in function of the latter and in antagonism to the action of the initial pressure stored in the balancing chamber, said initial pressure tending to reclose the obturator as soon as the pressure lowers in front of the piston in function of said drop of pressure.

According to an embodiment, the initial pressure is transmitted to the balancing chamber during the first part of the delivery stroke of the piston through a bypass conduit extending from the deliver chamber of the cylinder to said balancing chamber, said conduit being obturated by the piston itself at the end or the first part of its stroke and comprising a. check-valve which subsequently prevents the pressure from lowering in the balancing chamber.

Moreover, the pressure prevailing in the balancing chamber is maintained by a plunger projecting in said chamber through a fluid-tight guide and taking a bearing on a, calibrated spring arranged in a housing of the piston, which is compressed when the balancing chamber is initially placed under pressure, said spring then ensuring the compensation of the drop of pressure liable to take place therein during the second part of the delivery stroke of the piston by pushing back said plunger in function of said drop of pressure.

The obturator according to the present invention thus ensures a loss of pressure by throttling the fluid and is perfectly balanced, so that it constitutes, with its calibrated spring, a unit having its own very small suitably damped period. Its stroke is also very small, but uncovers very long orifices ensuring a sufficient outflow so that, during the second part of the piston stroke, the pressure remains constant on the upside of the obturator, that is to say in the delivery chamber of the cylinder.

The invention moreover presents numerous other features which are set forth in the following detailed description. It also includes, by Way of new industrial product, the landing shockabsorbers for airplanes to which said energy dissipating device is applied. These shock-absorbers ofier, in particular, the following advantages: a substantially constant reaction throughout the stroke; a reaction proportional to the energy to be absorbed (utilisation of the entire stroke whatever may be the energy) a slight resilient reaction ensuring, in combination with an accessory mechanical, pneumatic or hydraulic element, great smoothness in the suspension during rolling.

Embodiments of the subject-matter of the invention are illustrated, by way of examples, in the accompanying drawings.

Fig. 1 is a vertical section of a self-regulating energy dissipating device in accordance with the invention.

Fig. 2 is a cross section along line II-II of Fig. 1.

Figs. 3, 4, 5 and 6 are vertical sections illustrating detail modifications.

Figs. 7 and 8 illustrate, in vertical section, two landing shock-absorbers for airplanes.

According to Fig. 1, the self-regulating energy dissipating device comprises a cylinder l in which the energy dissipating fluid must pass from a chamber 2 to a chamber 3, which are separated by a piston 4 having a rod 5. The cylinder I is, for instance, secured to one of the constructional 9, recessed at H, has a solid bottom 12 projecting in the form of a plunger in a chamber Moreover a chamber I4 is provided below the flap-valve 8 and a light spring l5, taking a=bear ing on the bottom of said chamber I4, tends to u nsaid flap-valve against its seat M v perforated in thebottom of the'flap-valve put chamber 2 in communication with chamber .-A..plunger ll also projects into chamber l3 with: its bottom [8 turned towards the bottom I? of ;tai1piece"9'.' U I e V by means of a circular sole I3 on a calibrated spring 20ftakinga bearing, at'itsother end, on a seat. net the iston; Flutes 22, hollowed out iii .theiinne r wall of cylinder I' ensure a throttled communication between chamber 3 and chamber 2, u'p'to a certain. distance; above the lower dead centerbf the piston. "Moreov er, a by-pass conduit 23 leaves chamber 2fat 24,'substantiallyat the'Tu'pper level of the nutes zz', and opens into a.[ port'.25 of cylinder l'com'municatin'g with an orifice 26 of thepiston connected by .a pipe-line 21 28' to, chamber 13. of the pistqn. A'check-valve 29 having a spring 30 is interposed in said pipe- 1in '21,..2s,. 1 e '1 ,1 7 I LThe device' of"Figs. 1 and '2 I'oper'ats in the followin jmannerff e ;'when an f energy tends to push"piston sup-1 gt rui in. cylinder I, the. driving back for said piston creates" a pressure in the fluid contained inchamber 2. Said pressure is propagated under A the flap v'alve 8 through the holes [6. lvloreover, it is also" communicated, through the "by-pass" 23 aridpibe-lirie 21, 28, by opening the check lvalve 29; to chamber I3 inwh'ich it'racts, on ,th'one handlagainst the bottom .12 r the tail-piece or t:

flap-valve Band, on the, other hand, agairis't' the bottom |8 of piston I1. Consequently, piston l'l is'driven back, compressing its spring 20,,thefi flap-Waive 8 is held applied on its seat owing; to the fact that the pressurejpropagated undersaid valve through holes l6 'andin"chamber l3 bal arl'ces the pressure acting above it incharnber 2, Consequently, the liquid under pressure in cha'rn ber 2 can only pass into chamber 3,thr0l h the narrow flutes 22 in which it is throttled, the

cross' section and number of said flutes being such that for the initial speed of displacement of thepiston, a loss of head is obtained, which is proportional to thesquar eof said initial speed; The displacement of piston 4 in cylinder 1 is; therefore, considerably braked. When said 'pis ton has moved to the distance d,and.th'atf its bottom has risen to the position 3" abovaon the one hand, the upper "ends ofjfiutesl2 2I the other hand, the inlet 24 of by pa'ss 23, the fluid under pressure contained in chambr'2 canno longer flow through said flutes andsaid by-pass, so that the pressur 'tends to rise'in saidchamb'er, Asfcheck-valve 29 is n'olonger pushed backiby the, stream, it has closed and," consequently, tlre initially adjusted pressure is maintainedin' 'chanil be'r l3; It is therefore only-when the pressure created in chamber 2 becomes greater than that existing in said chamber l3, that flap-valve 8 will be pushed downwardly lifting more or less from Holes l6,

Said pistonl'l' takes a bearing A its seat 1 in function of the difference of said pressures. The fluid under pressure then passing between flap-valve 8 and its seat can directly enter chamber 3 by passing through ducts 3| passing through the piston.

But as soon as the pressure prevailing in chamber 2 tends to lower below the initially adjusted pressure in chamber l3, the latter pushes back the bottom l2 of the'tail-piece of flap-valve 8 which tends to close and, consequently, to cause the pressure in chamber 2 to rise by increasing the throttling. The fluid contained in chamber 2 can therefore flow through the ducts 3| only when the pressure prevailing in chamber 2 approximates that prevailing in chamber l3. The pressure existing inthis latter chamber is maintai'ned in case of a slight drop due to leakages through the plungeril'l' which has been initially driven back by the adjusted pressure in said chamberand which is pushedinto the latter 'by its spring in proportion sai'd pressure-tends to lower.

Consequently, in case of variations of the energ developed between the tvvo constructional elementsfbet'ween whichthe dissipating device is interposed, flap-valved? effects damped oscillat ing movements having. the efiect of more oriless;

opening or closing the'an'nular duct provided'livetween its truncated flange and its truncated seat, by thus throttling'the'section of passage-wayfor the liquid under pressure contained in chamber 2',

by the ducts' 3 I in function df said energy varia j tions, The dimensions'of flapkvalv e 8 are more-f over so calculated that the displacements thereof are very slight' 'relatiyely to the initial sagging of'spring' 20, so that thereactionof the latter, which fact regulates the pressure in chamber l3, 'remainsapproximatelyconstant, as wen as the pressure prevailing in chamber 2.

The weak spring l5"is intended to hold flap valve 8""applied against its 'seatin inoperative When piston 4 returns to its starting position: an annular flap-yalve '32 lifts from the end i 33' o ffpiston 4 and is retained by a flange 34 oithe latter, so that theliquid [can again pass frorfi chamber '3, through ducts"3l""a'ndducts 35, di rectlyf inf-chamber "2; ducts 35 are gauged in order to suitably check the' return stroke 'of pi's ton 4, inposition" of rest and as soon as the piston tends'to" rise, the annular flap-valve 32 presses against the part '33' of'fthe. piston and q m z g t as h V is In Fig. 3,, the flutes '22".'iirovi ded' within the cylinder according to Figfs'fl and ,2, are replaced by" a tube 36 lates outside cylinder l and to which it is" connected bylconnection's 31, 38. jrh inner diameter and profiles offsaid tube 36 are suchj that it fulfills the same function asf t h flutes. Its inner profile is, for instance, rough, in particular threaded, so as to obtain a loss of head proportional to the squareof the initial speed or t usmn v is. I Ac'cording'to' Fig. 4, the placing under pressure oi chamber 2 as well as chamber I3 cornm uni ating therewith, can bednitially. adjusted by compelling the liquid contained in said chamber t'o pa'ss through an orifice 3 9 of small cross,- sectibm arbitrarily adjusted'by means oi'a needle 40 "capable of b e ing screwed in an internally threaded membeif 41, the access to saidneedl'e being closed by a cover 42'." The liquid passing through the throttle 39 enters a duct 43 which leads it to chamber 3 in the same manner as conduit 36 of Fig. 3. The adjustment of said throttled cross-section allows of causing the pressure obtained in chamber 2 and, consequently, in chamber iii, to vary in function of another parameter than the initial speed, for instance in function of the bulk of the member the kinetic energy of which is to be absorbed, and said bulk can be, in the case of an airplane shock-absorber, the bulk of the latter.

According to a modification, regulating chamber 55 can be initially placed under pressure, not by a by-pass supplying liquid under pressure generated in chamber 2 in which acts the delivery of the piston, but by an extraneous source of fluid under pressure.

Fig. 5 shows an embodiment of this modification in which the orifice 26, leading by means of the pipe-line and check-valve 29 to chamber l3, cornmunciates through port 25 with a conduit M coming from an auxiliary cylinder iii in which the liquid is delivered by a piston 46 the rod 41 of which is rigid with a roller 48 taking a bearing on the ground by the side of the main wheel 49 supported by the main shock-absorber 59. A calibrated orifice 5! controls the access of the liquid to an overhead tank 52.

When the airplane lands, the roller 68 bears on the ground at the same time as the main wheel as, so that the piston 46 is pushed into its cylinder 55 parallel to the movements imparted to piston :i entering cylinder l of the main shockabsorber till. The liquid contained in cylinder 45 is driven, with a speed corresponding to the vertical speed of the airplane, through the throttle 5! into the tank 52. The throttle 5i creates in cylinder a pressure proportional to the square of the speed of passage, therefore to the square of the vertical speed of the airplane. Said pressure is transmitted to chamber 1 3 through conduit M, orifice 26, and pipe-line 21. In this case an adjustment of the pressure created in chamber 53 is therefore also obtained which is directly proportional to the square of the vertical speed of the airplane and, consequently, to the energy to be absorbed.

5 illustrates a modification in which the flap-valve t of Fig. 1 is replaced by a slide-valve 53 having ports 54. On the other hand, ports 55 are provided in the piston and communicate with the ducts When the slide-valve 53 lowers under the action of the pressure created in chamber 2 and in antagonism to the pressure prevailing in the self-regulating chamber 13, its upper edge first of all uncovers the upper ports 55 of the piston then, as it continues to lower, its own ports 5 more or less coincide with the other ports 55 of the piston. The slide-valve 53 comprises in its bottom orifices 56 fulfilling the same function as the orifices 55 of flap-valve 8. Moreover, the operation is identical to that described with reference to Fig. 1.

Fi '2 illustrate a hydro-mechanical shock-absorber for airplanes to which is applied the energy dissipating device.

shock absorber comprises at its ends a bail the airplane, and a ball 58 connected to the train of wheels. Ball 5i is rigid with a cylinder 59 telescopically engaging in a cylinder 56 rigid with ball Piston 6 of Fig. 1 is rendered rigid with cylinder Chamber 2 of Fig. 1 is illustrated by the interior of cylinder to and the enclosure 3 is placed between piston 6 and a diaphragm 6i freely sliding, by means of a cylindrical guide 62, in cylinder 59. By-pass 23 of Fig. 1 opens into chamser 2 at .2 5, as in said figure, and also comli'l, for instance connected to the frame of municates, as in the latter, through port 25 and check-valve 29, with the balancing chamber l3 in which project the tail-piece I I having a bottom it of flap-valve 8 and the plunger ll having a bottom is controlled by the spring 20. This part of the device therefore operates in an identical manner to the energy dissipating device of Fig. 1.

Furthermore, cylinder comprises a calibrated orifice 39 having an adjusting needle 40, accord ing to Fig. 4, which communicates through the tube is with a tube 63 leading to an annular tank 6 1.

This shock-absorber operates as follows:

At the beginning of the impact, cylinder 59 tends to lower into cylinder 6|], which drives the oil from chamber 2 into tank 64.

The pressure prevailing in chamber 2 acts on the underside of flap-valve 8, and, by propagating through holes 16, on the top of said flap-valve, as well as, in chamber l3, on the edge I2 of tailpiece H of said flap-valve. The flap-valve 8 has therefore no tendency to lift from its seat and the liquid is compelled to pass through the throttle 39 adjusted by the needle 40 in order to enter the closed cylindrical chamber 64. The passage of oil through the throttle 39 generates in chamber 2 a pressure which is proportional to the square of the speed of the liquid, therefore to the speed with which cylinder 59 is driven down, and which in its turn is function of the initial vertical speed of the airplane. Said pressure is transmitted, through the by-pass 23, to chamber 53 wherein it has for effect to push back the plunger ll, 18 and to compress spring 29.

After a given stroke of the piston 6, which is relatively small with respect to the entire stroke of the shock-absorber, the orifices 24 and 39 are ob'turated by piston 8, but the pressure prevailing in chamber [3 remains constant owing to the closing of valve 29 and the compensating action of spring 29 previously described. It results therefrom that the pressure necessary in chamber 2 for lifting the flap-valve 8 must be slightly greater than the pressure prevailing in chamber 93. When this higher pressure prevails in chamber 52, flap-valve 8 lifts and allows the liquid to pass, said liquid entering the enclosure 3 through conduits 3|.

Owing to the constant pressure prevailing in chamber t3, the pressure is maintained constant in chamber 2, flap-valve 8 automatically adjusting its opening according to the outflow of liquid to be ensured, in order that the pressure equilibrium should be maintained constant.

In the enclosure 3, the oil pushes back the diaphragm 9! which only acts for separating said oil from the air contained in cylinder 59 in order to avoid emulsions. Above said diaphragm 6|, cylinder 59 communicates with the atmosphere through orifices 65.

Furthermore, during the driving in of cylinder 59, the spring 66 placed around said cylinder is compressed, so as to ensure the operation when the shock-absorber returns to its normal position.

It is to be noted that the braking stress due to the throttling of the liquid being constant until the end of the stroke, spring 66 need not be sufficient for ensuring the suspension of the airplane under its own weight, and it is unnecessary for said spring to intervene in the shock-absorbing action upon landing.

This arrangement moreover has the advantage of resiliently storing a small proportion of the total energy and, consequently, of encountering but few difiiculties for ensuring the braking upon return and avoiding rebound.

In -order toensure the-smoothness of the suse liquid passes athrough; con

, With pension when rolling}:chamberl3 is not. come.

pletelyfluid-tight; :a slight leakage .isprovided: between piston l8 and its guide, said leakage being suflicientlyslight for the pressure to lower only to a slight extent during the :landing period,

but-it is suflici'ent for the pressure to be reduced at the end of a suitablettime. When said time has elapsed the pressure. has dropped: inschamben 13-, @which permits flap-valve 8 to allow the 1iquid topassaunder-slightapressure; Said leaks-l agacanbe provided-by arranging a helicalgroove 61 around rodl'l. i: i

u Ihez suspension is imainly -ensured -by.- spring 66v the return-.strokept which is braked .byv'the 1.

throttling ofrthe liquid produced by the calibrated -ducts 35. During rollin the shock absorber. is constantly driven in, s that orifices 24 and'39 are obturated.- 1

= Fig.= 8 illustrates an example-=of an airplane shock-absorber. whichicanbe, accordingto cir-.

hvi usthat can ec t applloationsin every case where it is necessary to a iustthe. ac icnaof. a-by rauli d ice. rans-,-

mitting any type of energy or acting in antagonismith etoam 1 were sinat Q-n evictin 11am;

Patent of thelmlifid S ates sha k, abso bers c zairplan si which comp s s a, cylinder, a piston, a delivery chamber anda re I ceiving; chamber in said cylinder, on each side of the piston, t pt n passa e twee a d.

hamb rs e d n t. ani termediate pa the. elivery. hamb one. passa f lar er c oss-w ction in; he pist n, adjustin obtur t rhave a ,in uSeat i-nasaidpis on o co trolli g thelast- I namedspassage, a balancing chamber in -thepiston, means-to admit in said balancing chamber a pressure holding ,theobturator appliedon itslseat in-antagonism to ;the,\ action of ,thevpressure ins the delivery chamber-during the, firstpartof the deliverystroke of rthe piston, thebalancingchamcumstances, a hydro-mechanical oroleo.-pneu+.-: v i

pa singwthe obturator and ,meansa closmgsaad matic shock-absorber; In contradistinction :to FigJl, use is made here of -a cylinder 59 telescopically entering a cylinder. 60 and a spring 65 placed around said cylinders and; taking: a-..beara ing onashoulder68of cylinderfills i i 1 Said sh'ock-absorbenutilises the slide-valve 53 of Fig; 6. 'Atthe beginning'of theoperation; .the

slide-valve 53 is completely balanced and remains closed; The liquid'is -therefore compelled to pass through the throttledorifice 59 -and then through the ducts which ensuresfithe initialsplacing under pressure of chamber 2-, pressure-which is transmitted to chamber-13 through themed'ium of-the'enclosureJl and pipeline ZG-to the checkvalve' '29. When the bottom 1-2 of the piston takes a bearing' on shoulderliiofcylinder 60-, en-' closure 11* isobturated;:so that the liquid is compelled to open the slide-valve 53- and to pass through the-ports 54, 55. Theopening pressure of said slide-valve is adjusted by the initial--pres-' sure prevailing 'inchamber: vI 3 and is maintained constant throughout the stroke, as explained in' the foregoing. The-liquid then passes through conduits 74 into the enclosure 3 wherein itis insulated from the atmosphereby a 'diaphragm 6|,

as in the preceding example. r e l v ln the" hydro-mechanical embodiment, the

chamber 15. communicateswith the atmosphere through orifices wand the suspension'is ensured bythespring 56. I In the ole o-pneumatic embodimentysprin'g-fifi, is done away with, as well asthe orificesjjj, so that chamber'15 is fluid-tight, Said chamber, therefore operates a pneumatic' -shockabsorber; the "initial" pressure prevailing therein, as well as the Volume thereojfyare calculated order o Obtain eptimu .,si spensipn, q n n ber ,being closed against-admitted, pressure when the -supply of pressure ,thereto is, cut off, :means 3 to-compensate theloss of pressure in the closed balancing chamber direct return channels ,by;

an e du ne- 0 ra a e.v on i ons- 2. An energy v dissipating, device fpr landing;

" an airplane, ,a pistonzconnectedhto another frame m mb o e a r a e, ,a'd l y i amb ran l,

a receiving: [chamber insaid cylinderon each side.v oi-sthe pistons-at least a throttling passage be:-

. wee dw h m s ien ne'a amin ermed ate. part org-the-delive 'yuchamber', at least, one pas aealo r a s o s-se ti n- -th i to auntie: justing Qbturater havinga seat in said piston for; controlling the last-named passage, a balancing chamber in ,the piston, a by-pass conduit leading r t e vd i er n ha e to aid b a ins ch m aidibye as epd n nt -s me n erim a part P wn h delive m ham e as l the tnrottungpa a e t be o ii at .ds mu ane slr, W fihs he. atte by-rth st ns at he and o th first -0mm rqkaa ch ckalv pr ven s nst p ure: f omrlq e na; n the. ba n in chamber when the supply of: pressure thereto-is;

ut-@fii-ta plu e rap ie ps n; said ba an n chamber, a bearing plateiorsa-id plunger,;a-,cali

m te p ing orti said. plate a dta m bearin s t o r ndaona seat Q t e pis on: a i al groove a und p un r itoie oris e .a slightlleakage-betweensaid plunger and its guide, direct return channels by-passing the obturaton wea enm lai fia rv ve91 ns sai cc nne ur nsshet sa or i al.- 1 :1

3. An energy dissipating deyicenaccordi t0 claim- 2, comprising; a- ;charnber, provided below the-obturator, alight spring taking a bearing on the bottomof -said chamber and-pushing the ob: u a e fis. eat, and s-in h abot m. of said obturaton 1 t i, 1, flnAn zenergy dissipating device .for landing shoal; absorbers 9i air-planes which comprises a cylinder rigidly connected-to a frame -member or? an airplane,=a piston connectedto-another frame member or theairplana a, hollow bottom and, a conicaltseat in; said piston, a nelivery charnbei ap la w r n ch mberi -sai winds on. ach side of the piston, at least a throttling passage between said chambers ending at an intermediate part of the delivery chamber, at least one pas- I meadow? pf invention; man other sage of larger cross-section in the piston, an adjusting obturator having a seat in said piston for controlling the last-named passage, a balancing chamber in the piston, a tail-piece integral with said obturator and provided with a recess and a solid bottom projecting as a plunger in said balancing chamber, a by-pass conduit leading from the delivery chamber to said balancing chamber, said by-pass ending at the same intermediate part of the delivery chamber as the throttling passage to be obturated simultaneously with the latter by the piston itself at the end of the first part of its stroke, a check-valve preventing the pressure from lowering in the balancing chamber when the supply of pressure thereto is cut off, a plunger projecting in said balancing chamber, a bearing plate for said plunger, a calibrated spring supporting said plate and taking a bearing, at its other end, on a seat of the piston, an helical groove around plunger to provide a slight leakage between said plunger and its guide,

direct return channels by-passing the obturator and an annular flap-valve closing said channels during shock absorbing.

5. An energy dissipating device for landing shock absorbers of airplanes, which comprises a cylinder rigidly connected to a frame member of an airplane, a piston connected to another frame member of the airplane, a delivery chamber and a receiving chamber in said cylinder on each side of the piston, a profiled tube having a rough inner wall so as to provide a throttled communication between said chambers and to obtain a loss of head proportional to the square of the initial speed of the piston, said profiled tube being connected to an intermediate part of the delivery chamber, at least one passage of larger cross-section in the piston, an adjusting obturator having a seat in said piston for controlling the last-named passage, a balancing-chamber in the piston,

means to generate in said balancing chamber a pressure holding the obturator applied on its seat in antagonism to the action of the pressure in the delivery chamber during the first part of the delivery stroke of the piston, means closing the balancing chamber when the supply of pressure thereto is cut off, means to compensate the loss of pressure in the closed balancing chamber, direct return channels by-passing the obturator and means closing said channels during shock absorbing.

6. An energy dissipating device according to claim 5, comprising in the connection between the profiled tube having a rough inner wall and the delivery chamber an orifice of small crosssection and provided with an adjusting needle, which is screwed in an internally threaded part.

7. An energy dissipating device for landing shock absorbers of airplanes, which comprises a cylinder rigidly connected to a frame member of an airplane, a piston connected to another frame member of the airplane, a delivery chamber and a receiving chamber in said cylinder on each side of the piston, at least a throttling passage between said chambers ending at an intermediate part of the delivery chamber, at least one passage of larger cross-section in the piston, a slidevalve having ports and sliding in said piston for controlling the last-named passage through ports provided in the piston which are progressively uncovered by said slide-valve and its ports, a balancing chamber in the piston, means to generate in said balancing chamber a pressure holding the obturator applied on its seat in antagonism to the action of the pressure in the delivery chamber during the first part of the delivery stroke of the piston, means closing the balancing chamber when the supply of pressure thereto is out 01f, means to compensate the loss of pressure in the closed balancing chamber, direct return channels by-passing the obturator and means closing said channels during shock absorbing.

8. A shock absorber for airplanes provided with an energy dissipating device according to claim 1, which comprises a cylinder connected to the frame of the airplane and rigid with a piston, a second cylinder connected to the train of wheels and in which the first-named cylinder and said piston are slidingly engaged, a delivery chamber in the second cylinder, a diaphragm freely sliding in the first cylinder, a cylindrical guide for said diaphragm, a receiving chamber in the first cylinder between the piston and the sliding diaphragm, a chamber communicating with the atmosphere above said sliding diaphragm in the first cylinder, an annular tank around the second cylinder, a connection between the delivery chamber and said tank, a calibrated orifice provided with an adjusting needle in said connection, a compression spring between a flange of the first cylinder and a seating on the second cylinder.

9. A shock absorber for airplanes having an energy dissipating device, which comprises a cylinder connected to the frame of the airplane and rigid with a piston, a second cylinder connected to the train of wheels and in which the first-named cylinder and said piston are slidingly engaged, a delivery chamber in the second cylinder, a diaphragm freely sliding in the first cylinder, a cylindrical guide for said diaphragm, a receiving chamber in the first cylinder between the piston and the sliding diaphragm, a chamber communicating with the atmosphere above said sliding diaphragm in the first cylinder, throttled orifice and ducts between the delivery chamber and the receiving chamber, at least one conduit of larger section in the piston, a slidevalve having ports and sliding in said piston for controlling the conduit of larger section through ports provided in the piston which are progressively uncovered by said slide-valve and its ports, a balancing chamber in the piston, a space around the piston, with a pipe-line controlled by a check-valve, transmitting the pressure generated in the delivery chamber to the balancing chamber, a shoulder in the second cylinder to limit the stroke of the piston, a compression spring between a flange oi the first cylinder and a seating on the second cylinder.

GASTON CHAUSSON.

REFERENCES CITED The following referenlces are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,112,705 Kinkaid Oct. 6, 1914 2,352,401 OConnor June 27, 1944 2,363,308 Focht NOV. 21, 1944 FOREIGN PATENTS Number Country Date 408,592 Britain Apr. 5, 1934 673,485 France Oct. 8, 1929 

